This page outlines the changes and known limitations associated with different versions of EASE-Grid. The original version of EASE-Grid was released in 1992 and the latest version, EASE-Grid 2.0, was defined in 2011. Table 1 summarizes the differences between the two versions.
|Feature||Original EASE-Grid||EASE-Grid 2.0|
|Projection ellipsoid||International 1924 Authalic Sphere||WGS 84|
|Pole location||Center of cell||Intersection of center cells|
|Scale (data-set specific)||Azimuthal/Cylindrical coupled (such as Nl/Sl/Ml 25.067525 km)||Azimuthal: Exact (such as 25.0 km or 36.0 km)
Cylindrical: Integer-multiples across latitude of true scale
|Dimensions||Odd-numbered (721 x 721)||Even-numbered (720 x 720)|
|Nested Grids||Must choose between total coverage and nested cells||Coverage can stay the same, only number of cells changes|
|Corner Points||Corner cell locations in azimuthal grids are undefined||No undefined corner cells|
|GeoTIFF||Requires reprojection||Supported without reprojection1|
|Software Issues||Usually requires user to understand custom projection settings||Most software supported1|
|1 Achieved by setting projection ellipsoid to reference datum
Table 2 summarizes the current state of support for EASE-Grid format data when used with current popular software packages. Table 2 also lists geodetic parameter data set codes from the European Petroleum Survey Group (EPSG) for both the original EASE-Grid and 2.0 versions. EPSG codes are helpful shortcuts for PROJ.4 software, and for software that depends on PROJ.4, such as GDAL Tools.
(WGS 84 Projection)
|Supported||Cylindrical projection is supported. Azimuthal is not supported.||HDF depends on GCTP. NSIDC may propose a change to GCTP to support Lambert Azimuthal with ellipsoid.|
|PROJ.4||Supported||Azimuthal and cylindrical EASE-Grid 2.0 supported in PROJ 4.8.0 (13 March 2012). Azimuthal projection was supported in PROJ 4.7.0 (23 September 2009). Bug in PROJ 4.7.0 resulted in error of ~15 km when transforming points near equator for cylindrical EASE-Grid 2.0 data.||Both original EASE-Grid and EASE-Grid 2.0 are fully supported as of PROJ 4.8.0 (13 March 2012).|
|GDAL Tools||Supported||Supported, with correct version of PROJ.4.||User must ensure correct PROJ.4 is installed; see PROJ.4 notes.|
|EPSG Codes||North: 3408
Note1: Use these ProjectedCRS Codes for EPSG Version 8.6 or later.
Note2: GDAL tools built with the correct version of PROJ4 will work on the EASE-Grid 2.0 projections with PROJ4 strings even if it's built with EPSG Codes earlier than 8.6.
|PROJ 4.8.0 is required to obtain correct values for EASE-Grid 2.0 cylindrical.|
T. Haran (NSIDC) has written procedure to add cylindrical equal-area to ENVI. Requires simple modifications to support header information for EASE-Grid data sets. ENVI cannot read/write user-defined projection information from/to GeoTIFF, but it can do so with its own ENVI header format.
Cylindrical equal-area requires user-defined projection information; simple modifications to support header information for EASE-Grid 2.0 data sets are forthcoming.
|Simple modifications are required for cylindrical equal-area in both EASE-Grid versions; see respective column for current status.
Page last updated: 06/29/15